Air conditioning



July 18, 1950 i r. K. sHl-:Rwool:v 2,515,319

AIR CONDITIONING Filed Nov. 22, 1946 2 sheets-sheet 1 IN V EN TOR.

July 18, 1950 T. K. sHl-:Rwoony AIR CONDITIONING Filed Nov. 22, 1946 2 Sheets-Sheet 2 Patented July 18, 1950 AIR CONDITIONING Thomas K. Sherwood, Wellesley Hills,

signor to Servei, Inc., New York, N. Y., a corporation of Delaware Application November 22, 1946, Serial No. 711,703

' 8 Claims. (Cl. 62-5) This invention relates to air cooling with an absorption refrlgerating apparatus and more particularly to reducing superheating of refrigerantabsorbent solution in the generator of such apparatus.A

In the operation of certain types of absorption refrigerating apparatus, particularly low pressure or vacuum types, it has been found that under certain conditions of operation excessive superheating resulting in noisy boiling of the solution may occur in the generator on starting the apparatus. It has been found in practice that by diluting the solution in the generator, as by providing a return line for conveying liquid refrigerant from the evaporator to the generator, that superheating may be greatly reduced. With this arrangement when the apparatus is shut down the liquid refrigerant remaining in the evaporator drains directly to the bottom of the generator, diluting the solution therein, so that when the apparatus is later started up the solution boils more readily whereby superheating and its ensuing nose is reduced. This arrangement for diluting the solution in the bottom of the generator following a shut-down operates very satisfactorily provided liquid refrigerant is supplied to substantially all of the evaporator tubes immediately prior to the shut-down. However, should the unit operate for a period of time `on half heat input, for instance, before being shut down, the lower tubes of the evaporator become dry and warm, so that liquid refrigerant draining from the upper to the lower tubes following a shut down is vaporized in the lower tubes and little or no liquid refrigerant reaches the bottom of the evaporator, so that substantially no liquid refrigerant is delivered to the bottom of the generator as desired.

It is therefore an object of this invention to provide means whereby it is assured that diluted refrigerant-absorbent solution will be present in the bottom of the generator of an absorption refrigerating apparatus following each shut-down of the apparatus.

Although various means may be utilized to accomplish the above object, I choose to use a control arrangement whereby at the beginning of a shut-down Vperiod the refrigerating apparatus continues to supply liquid refrigerant to the evaporator or cooling element-for a short period of y time after the circulation of air over the evaporator has been stopped. With this arrangement, since air to be cooled is no longer circulated -over the evaporator, the liquid refrigerant that is supplied to the evaporator passes there- 2 through without appreciable vaporization, which liquid is collected at the lower part of the evaporator and conveyed to thev bottom of the generator, thereby diluting the refrigerant-absorb- -ent solution in the generator following each shutdown period.

'I'he invention together with its objects and advantages is set forth in more technical detail in the following description and accompanying drawings, wherein:

Fig. 1 is aview diagrammatically illustrating an air conditioning system incorporating this invention;

Fig. 2 is an elevational view, partly in section, shxwing an air cooling element and drip trough; an

Fig. 3 is a view diagrammatically illustrating my improved electric circuits and controls, for controlling the operation of the air conditioning system illustrated in Fig. 1.

Referring to Fig. 1, the air cooling system includes an evaporator or cooling element l0 arranged in a duct system through which air is drawn from an enclosure Il and after being cooled is returned to the enclosure. The duct system includes a duct l2 through which air is withdrawn from the enclosure and in which is disposed a filter I3 and the cooling element I0. Air is drawn through duct I2 by 'a blower 55 from which air is discharged through a duct Il to the enclosure. The blower vis operated by an electric motor 56.

The cooling element IU forms part of a refrigerating apparatus of the two pressure absorption type and may be of the type disclosed in U. S. Patent No. 2,282,503, to A. R. Thomas and P. P. Anderson, Jr. In an apparatus of this type liquid refrigerant, such as, for example, water, is introduced into the upper part of the evaporator or cooling element I0 from a condenser I5 through a path of ilow including a conduit I6 and a flash chamber, not shown. 'I'he liquid refrigerant vavporizes in cooling element I0 with consequent Y conducted from absorber I1 to a generator I8 in duit 20, an annular stabilizing vessel 2l and a conduit 22 into the bottom of the generator.

Within the generator are disposed a plurality of riser tubes enveloped by a chamber formed by an outer shell 23 to which steam is supplied through a conduit 24 from a boiler 25. The heating of the riser tubes by the steam causes refrigerant vapor to be expelled from the absorption solution, the expelled vapor being effective to raise absorption solution by gas or vapor-lift action. 'I'he expelled vapor passes through the upper ends of the riser tubes into a vapor separator 26 and thence ows through a conduit 21 to condenser I 5 in which the vapor is liquefied. The l liquid refrigerant formed in the condenser ows through conduit I6 to the upper part of cooling refrigerating cycle. The concentrated absorption solution from which refrigerant vapor has been expelled is conducted from the upper part of generator I8 to absorber I1 through a path of flow including a conduit 28, a second passage of the liquid heat exchanger and conduit 29 into the top of the absorber.

The disclosure in the aforementioned Thomas and Anderson patent may be considered as being incorporated in this application, and, if desired,

` reference may be made thereto for a detailed description of the refrigerating apparatus.

The condenser I5 and absorber I1 constitute heat rejecting parts of the refrigerating apparatus and are cooled by a suitable cooling medium such as, for example, water', which is continuously circulated in a closed circuit through a spray-type cooling tower 30. The cooled water is conducted through a conduit 3l into and through banks of tubes 32 within the absorber, whereby heat,resulting from absorption of reelement I0, as explained above, to complete the frigerant vapor by liquid absorbent, is given up to the cooling water. The water is conducted from the absorber through a conduit 33 to the condenser in which heat of condensation; resulting from condensation of refrigerant vapor, is

given up to the cooling water.

The cooling water flows from the condenser through a conduit 34 to spray nozzles disposed in the upper part o1' the cooling tower, one of which nozzles is indicated at 35. Thewater passing downward in tower 30 flows in intimate contact with an upwardly iiowing stream of air which is drawn through inlets 36 by a fan 31, and exhausted or discharged from the upper part of the cooling tower at an outlet 38. The fan 31 is arranged to be driven by an electric motor indicated at 39. The water, which iscooled by partial evaporation into the upwardly flowing air stream in tower 30, collects in a sump at the bottom of the tower and is conducted therefrom through conduit 3l to the absorber by a pump 43 operated by an electric motor 4I.

pump 48 operated by an electric motor 49.

As shown in Fig. 2 of the drawing, the evapoy is returned' through a conduit 41 to the steam boiler by a rator or cooling element III includes a plurality of rows of horizontal tubes 50 arranged in vertical spaced relation and provided with heat tran'sfer ns 5I. Each of the tubes 50 is provided at one end with a cup 52 which receives liquid refrigerant from the tube above. A drain trough 53, connected to the bottom of the generator I8 by a conduit 54, is located immediately below the ends of the lowermost row of tubes 58. The arrangement is such that liquid refrigerant flows from the condenser through conduit I6 into a ash chamber, not shown. From the ash chamber the liquid refrigerant flows into the uppermost row of Vtubes 50, through these tubes, into the cups a the end of the next lower row of tubes and so 'on through the remaining tubes in series. The refrigerant vapor formed in the evaporator tubes flows from the ends thereof into headers, not shown, at each end of the evaporator, and from there' the vapor flows into the absorber. Any liquid refrigerant that is not vaporized in the lowermost row of tubes fiows from the outletv ends thereof into drain trough 53, and fromsthere the liquid refrigerant ows through conduit 54 into the bottom of generator I8.

Referring now to Fig. 3 of the drawing wherein my improved delayedaction control is diagrammatically illustrated, 51 designates a manually operated main switch which is connected on Aone side to a source of alternating current by a conductor 58 and on the other side this switch is connected by a conductor 58 to one terminal of the :primary winding 59 of a step-down transformer 68. The opposite terminal of the primary winding is connected to the source of alternating current by conductors 6I and 62. One terminal of the secondary or low voltage winding 63 of the transformery is connected by a conductor 64 to one terminal of a thermostatic switch 65. This thermostatic switch, which is contained in a room thermostat diagrammatically illustrated at 65 in Fig. 1, may be of any suitable type. However, it is preferred to use a thermostatic switch which opens and closes the low voltage circuit in accordance with the temperature of the enclosure that is being conditioned. Such a switch is illustrated and described in Patent No. 2,381,427 to Sven W. E. Andersson. and, if desired, reference may be had to this patent for a detailed description of this switch. The opposite terminal of thermostatic switch 65 is connected by a conductor 66 to one side of a relay 61, and the opposite side of this relay is connected by a conductor 68 to the second terminal of the low voltage winding 63 of the transformer. Thus, a rst low voltage circuit includes the secondary winding 63 of the transformer, conductor 64, thermostatic switch 65, conductor 66, relav 61 and conductor 68. An electric heating coil 69 is connected across this rst low voltage circuit by conductors 10 and 1I.

A second low voltage circuit includes the seconda-ry winding 63 of the transformer, conductor 6^. a conductor 12, solenoid 44, a conductor 13, a thermostatic switch 14 and a conductor 15. A relay 16 is connected across this second low voltage circuit by conductors 11 and 18. 'I hermostatic switch 14 includes a bi-metal element that is arranged to be heated by heating coil 69 to close the switch when the heating element is energized. Thebi-metal element has'a given heat capacity, so that switch 14 remains closed for a friven period of time after the heating coil 66 has been deenergized.

Referring still to Fig. 3, a conductor 19, a

switch 80 operated by relay 01 and a conductor 8l connect one side of the blower motorl 5l to high voltage conductor Il', the opposite side oi which motor is connected directly to conductor 62 of the high voltage circuit.V -A conductor $2, a switch 83 operated by relay 1l and a conductor 84 connects one side of cooling tower fan motor 39 to high voltage conductor Il' and the opposite side of the i'an motor is connected by a conductor 85 to conductor I! of the high voltage circuit. As shown, cooling tower pump motor 4| is connected in parallel with fan motor $9 by conductors 85 and 81.

Assuming that the enclosure Il is above the desired temperature and that main switch 51 is closed, thermostatic switch 55 closes the circuit in the first low voltage circuit and low voltage current flows from secondary winding 63 of the transformer through conductor, thermostatic switch 65, conductor 66, relay 51 and conductor 68 thereby energizing relay 61. The energization of relay 61 causes switch 80 to be closed thereby energizing the .blower motor 56. With thermostatic switch B5 closed, low voltage current flows also through conductor 10, heating coil 69 and conductor 'H whereby the heating coil is energized'which in turn heats the -bi-metal element of switch 'I4 causing this switch to Aclose the second low voltage circuit. The closing of the second low voltage circuit energizes the sole- ,noid 44 of the gas burner 'control whereby fuel gas is supplied to the gas burner 43 of the steam boiler which in turn supplies steam to the generator I8 causing refrigerant vapor to be ex` pelled from solution, which vapor is liquefied in the condenser and the liquid is vaporized in the evaporator producing the desired cooling effect, as explained above. The closing of the second low voltage circuit also energizes the relay 16 which closes switch 83 whereby the cooling tower fan motor 39 and pump moto;` 4I are energized and cooling Iwater is supplied to the absorber and condenser.

Assume now that the enclosure Il has reached the desired low temperature and that thermostatic switch 65 opens the rst low voltage circuit, relay Bl is deenergized and switch 80 is opened, which in turn denergizes blower motor 56. The opening of the ilrst low voltage circuit also deenergizes the heating coil 69 so that the bi-metal element of switch 14 is no longer heated by this coil. However, as explained above, the .bi-metal element has suncient heat capacity so that switch 'I4 in the second low voltage cir. cuit remains closed for a given period of time after switch 65 in the first low voltage circuit has been opened. By providing a suitable heat capacity in the form of a block of metal, for instance, associated with the bi-metal element, any desired interval of time may be provided between the cessation of current in the first low voltage circuit and the opening of switch 14 in the second low voltage circuit.

At the beginning of a shut-down period, with switch 65 open and switch l4 closed, refrigerant vapor will continue to be Aexpelled from solution in the generator, liqueiied in the condenser and the liquid refrigerant will be conveyed to the evaporator, as before. However, since the blower is now idle, most of the liquid refrigerant supplied to the evaporator vwill pass therethrough as liquid and .be caught in the drain trough 53. Also, when switch 'I4 finally opens the second low voltage circuit and deenergizes solenoid 44 and relay 'I6 thereby stopping the ref-n irigerating cycle, any liquid refrigerant that remains in the tubes of the evaporator will ow downward therethrough into trough Il. From the trough the liquid refrigerant is conveyed through conduit 54 into the bottom of the generator. In this manner it is 'assured that the solution in the bottom of the generator will be diluted after each shut-down so that when the unit is again started up the solution will boil more readily, without superheating and without no se.

Having thus disclosed my invention, I wish it to be understood that I do not desire. to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

What is claimed is:

1. 4A refrigerating apparatus comprising a generator, a condenser, an evaporator, an absorber, conduits interconnecting said elements for flow of a refrigerating medium and an absorption solution, a nrst means for heating said generator,

a second means for cooling said condenser and absorber, a third means for flowing a medium to be cooled in heat exchange relation with said evaporator, and means for controlling the operation of said rst and third means, said con-v trol means including mechanism for discontinuing the operation of said thirdmeans while continuing the operation of said first means for a short period of time, whereby liquid refrigerant supplied to the evaporator after the operation of the third means has been discontinued flows therefrom as liquid refrigerant, and means for conveying said liquid refrigerant as such from the evaporator to the bottom of the generator.

2. A refrigerating apparatus comprising a generator, a condenser, an evaporator, an absorber, conduits interconnecting said elements. for ilow of a refrigerating medium and an absorption solution, a. first means for heating said generator, a second means for cooling said condenser and absorber, a third means for flowing a medium to be cooled over said evaporator, and means for' controlling the operation of said rst, second and third means, said control means including mechanism for discontinuing the operation of said third means while continuing the operation of said irst and second means for a short period of time, whereby liquid refrigerant supplied to the evaporator after the operation of the third means has been discontinued ows therefrom as liquid, and means for conveying said liquid from the evaporator directly to the bottom of the generator.

3. An air conditioning system comprising a blower, a refrigerating unit including a generator, a condenser, an evaporator, an absorber, conduits interconnecting said elements for ilow of a refrigerating medium and an absorption solution, an additional conduit connected between the evaporator and the generator for flow of liquid refrigerant from the former to the latter,

means for heating said generator, means -for cooling said condenser and absorber, a control for the blower, the generator heating means and the absorber and condenser cooling means, said control being operable responsive to a change in temperature of air being conditioned, andmechanism associated with aid control for'continuing the operation of the generator heating means and the absorber and condenser cooling means for a short period of time after the blower has been stopped, whereby liquid refrigerant supplied to the evaporator after the blower has been stopped flows therefrom to the bottom of the generator thereby diluting solution contained therein. i

4. In an air conditioning system, an absorption refrigerating apparatus comprising a generator, a condenser, an evaporator, an absorber and conduits interconnecting said elements for flow of a refrigerating medium and an absorption solution, a steam boiler for supplying steam to said generator, a gas burner for heating said boiler, means for controlling the supply of gas to said burner, means for supplying a cooling medium to said condenser and absorber, a blower for conveying air to be cooled over said evaporator, control means operable responsive to the temperature of an enclosure being cooled for stopping said blower while continuing the supply of gas to said burner and the supply of cooling medium to said condenser and absorber for a limited period of time, whereby liquid refrigerant supplied to said evaporator after the blower has been stopped flows therefrom as liquid, and means for conveying said liquid directly to the bottom of said generator,

5. An air conditioning system comprising an absorption refrigerating apparatus, said apparatus including a generator adapted to contain a refrigerant-absorbent solution, means for heating said generator to expel refrigerant vapor from solution, a condenser connected to said generator to receive refrigerant vapor therefrom, means for cooling said condenser, an evaporator connected to said condenser to receive liquid refrigerant therefrom and a conduit connecting the evaporator directly to a lower portion of the generator for ow of liquid refrigerant from the former to the latter, an air duct in which said evaporator is located, a blower for forcing air through said duct in heat exchange relation with said evaporator, and means for controlling the operation of the generator heating means, the condenser cooling means and the blower, said control means including a delayed action mechanism so constructed and arranged that the generator heating means and condenser cooling means continue to operate for a short interval of time after the blower has been stopped, whereby liquid refrigerant supplied to the evaporator after the blower has stopped flows therefrom to the lower portion of the generator thereby diluting the solution contained therein. l

6. An air conditioning system comprising an absorption refrigerating apparatus, said apparatus including a generator adapted to contain a refrigerant-absorbent solution, means for heating said generator to expel refrigerant vapor from solution, a condenser connected to said generator to receive refrigerant vapor therefrom, means for cooling said condenser, an evaporator connected to said condenser to receive liquid refrigerant therefrom and a conduit connecting the evaporator directly to a lower portion of the generator for flow of liquid refrigerant from the former to the latter, an air duct in which said evaporator is located, a blower for forcing air through said duct in heat exchange relation with said evaporator, and means for controlling the operation of the generator heating means and the blower, said control means including a first thermostatl for energizing and deenergizing said blower and which thermostat operates responsive to changes in the temperature of air being conditioned, and a second thermostat for energizing and deenergizing the generator heating means, said second thermostat being operable in timed relation with and responsive to the operation of the rst thermostat, whereby liquid refrigerant supplied to the evaporator after the blower has been deenergized flows therefrom to the lower portion of the generator thereby diluting the solution contained therein.

7. An air conditioning system comprising an absorption refrigerating apparatus, said apparatus including a generator adapted to contain a refrigerant-absorbent solution, means for heating said generator to expel refrigerant vapor from solution, a condenser connected to said generator to receive refrigerant vapor therefrom, means for cooling Isaid condenser, an evaporator connected to said condenser to receive liquid refrigerant therefrom and a conduit connecting the evaporator directly to a lower portion of the generator for flow of liquid refrigerant from the former to the latter, an air duct in which said evaporator is located, a blower for forcing air through said duct and over said evaporator, and means for controlling the operation of the generator heating means, the condenser cooling means and the blower, said control means including a iirst low voltage circuit for energizing and deenergizing said blower and which circuit is opened and closed responsive to the temperature of air being conditioned, and a second low voltage circuit for energizing and deenergizing the generator heating means and the condenser cooling means, said second low voltage circuit being opened and closed in timed relation with and responsive to the opening and closing of the first low voltage circuit, whereby liquid refrigerant supplied to the evaporator after the blower has been deenergized flows therefrom to the lower portion of the generator thereby diluting the solution contained therein.

8. In the art of conditioning air by the aid of a heat operated refrigerating system, that improvement which includes expelling refrigerant vapor from a refrigerant-absorbent solution in a place of vapor expulsion thereby concentrating the solution, liquefying the expelled refrigerant vapor, conveying the liquefied refrigerant to a place of vaporization, owing air to be cooled in heat exchange relation with the place of vaporization whereby the liquid refrigerant is vaporized and `the air is cooled, absorbing the vaporized refrigerant into the concentrated absorbent solution thereby diluting the solution, owing the diluted solution to the place of vapor expulsion, discontinuing the flow of air in heat exchange relation with the place of vaporization while continuing to convey liquefied refrigerant thereto, flowing the liquefied refrigerant through and from the place of vaporization as liquid, and conveying said liquid to the place of vapor expulsion whereby the diluted solution contained therein is further diluted.

THOMAS K. SHERWOOD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,981,952 Foss Nov. 27, 1934 2,061,606 Zellhoefer Nov. 24, 1936 2,352,814 Thomas July 4, 1944 2,392,894 Zwickl Jan. l5, 1946 2,399,922 Grossman May 7, 1946 2,469,142 Andersson May 3.' 1949 

